https://github.com/python/cpython/commit/cdca0ce0ad47604b7007229415817a7a152f7f9a
commit: cdca0ce0ad47604b7007229415817a7a152f7f9a
branch: main
author: Barney Gale <[email protected]>
committer: barneygale <[email protected]>
date: 2024-01-09T23:04:14Z
summary:
GH-113528: Deoptimise `pathlib._abc.PurePathBase.relative_to()` (again)
(#113882)
Restore full battle-tested implementations of `PurePath.[is_]relative_to()`.
These were recently split up in 3375dfe and a15a773.
In `PurePathBase`, add entirely new implementations based on `_stack`, which
itself calls `pathmod.split()` repeatedly to disassemble a path. These new
implementations preserve features like trailing slashes where possible, while
still observing that a `..` segment cannot be added to traverse an empty or `.`
segment in *walk_up* mode. They do not rely on `parents` nor `__eq__()`, nor do
they spin up temporary path objects.
Unfortunately calling `pathmod.relpath()` isn't an option, as it calls
`abspath()` and in turn `os.getcwd()`, which is impure.
files:
M Lib/pathlib/__init__.py
M Lib/pathlib/_abc.py
diff --git a/Lib/pathlib/__init__.py b/Lib/pathlib/__init__.py
index 26e14b3f7b2005..ccdd9c3d547c8e 100644
--- a/Lib/pathlib/__init__.py
+++ b/Lib/pathlib/__init__.py
@@ -11,6 +11,7 @@
import posixpath
import sys
import warnings
+from itertools import chain
from _collections_abc import Sequence
try:
@@ -254,10 +255,19 @@ def relative_to(self, other, /, *_deprecated,
walk_up=False):
"scheduled for removal in Python 3.14")
warnings.warn(msg, DeprecationWarning, stacklevel=2)
other = self.with_segments(other, *_deprecated)
- path = _abc.PurePathBase.relative_to(self, other, walk_up=walk_up)
- path._drv = path._root = ''
- path._tail_cached = path._raw_paths.copy()
- return path
+ elif not isinstance(other, PurePath):
+ other = self.with_segments(other)
+ for step, path in enumerate(chain([other], other.parents)):
+ if path == self or path in self.parents:
+ break
+ elif not walk_up:
+ raise ValueError(f"{str(self)!r} is not in the subpath of
{str(other)!r}")
+ elif path.name == '..':
+ raise ValueError(f"'..' segment in {str(other)!r} cannot be
walked")
+ else:
+ raise ValueError(f"{str(self)!r} and {str(other)!r} have different
anchors")
+ parts = ['..'] * step + self._tail[len(path._tail):]
+ return self._from_parsed_parts('', '', parts)
def is_relative_to(self, other, /, *_deprecated):
"""Return True if the path is relative to another path or False.
@@ -268,7 +278,9 @@ def is_relative_to(self, other, /, *_deprecated):
"scheduled for removal in Python 3.14")
warnings.warn(msg, DeprecationWarning, stacklevel=2)
other = self.with_segments(other, *_deprecated)
- return _abc.PurePathBase.is_relative_to(self, other)
+ elif not isinstance(other, PurePath):
+ other = self.with_segments(other)
+ return other == self or other in self.parents
def as_uri(self):
"""Return the path as a URI."""
diff --git a/Lib/pathlib/_abc.py b/Lib/pathlib/_abc.py
index c16beca71aa7c7..5caad3c0502399 100644
--- a/Lib/pathlib/_abc.py
+++ b/Lib/pathlib/_abc.py
@@ -3,7 +3,6 @@
import posixpath
import sys
from errno import ENOENT, ENOTDIR, EBADF, ELOOP, EINVAL
-from itertools import chain
from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR,
S_ISFIFO
#
@@ -358,24 +357,40 @@ def relative_to(self, other, *, walk_up=False):
"""
if not isinstance(other, PurePathBase):
other = self.with_segments(other)
- for step, path in enumerate(chain([other], other.parents)):
- if path == self or path in self.parents:
- break
+ anchor0, parts0 = self._stack
+ anchor1, parts1 = other._stack
+ if anchor0 != anchor1:
+ raise ValueError(f"{str(self)!r} and {str(other)!r} have different
anchors")
+ while parts0 and parts1 and parts0[-1] == parts1[-1]:
+ parts0.pop()
+ parts1.pop()
+ for part in parts1:
+ if not part or part == '.':
+ pass
elif not walk_up:
raise ValueError(f"{str(self)!r} is not in the subpath of
{str(other)!r}")
- elif path.name == '..':
+ elif part == '..':
raise ValueError(f"'..' segment in {str(other)!r} cannot be
walked")
- else:
- raise ValueError(f"{str(self)!r} and {str(other)!r} have different
anchors")
- parts = ['..'] * step + self._tail[len(path._tail):]
- return self.with_segments(*parts)
+ else:
+ parts0.append('..')
+ return self.with_segments('', *reversed(parts0))
def is_relative_to(self, other):
"""Return True if the path is relative to another path or False.
"""
if not isinstance(other, PurePathBase):
other = self.with_segments(other)
- return other == self or other in self.parents
+ anchor0, parts0 = self._stack
+ anchor1, parts1 = other._stack
+ if anchor0 != anchor1:
+ return False
+ while parts0 and parts1 and parts0[-1] == parts1[-1]:
+ parts0.pop()
+ parts1.pop()
+ for part in parts1:
+ if part and part != '.':
+ return False
+ return True
@property
def parts(self):
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